Bug 137323 – Fail better when is<>() / downcast<>() is used for an unsupported type

• Component: DOM
• Status: RESOLVED FIXED

[Chris Dumez]

We should fail better when is<>() / downcast<>() is used for an unsupported type (i.e. a type that doesn't have the needed TypeCastTraits template specialization).

Currently, we get an obscure linking error, which is sub-optimal.

[Chris Dumez]

Created attachment 239067 [details]
Patch

[Chris Dumez]

Comment on attachment 239067 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=239067&action=review

> Source/WTF/wtf/TypeCasts.h:42
> +        static_assert(std::is_void<ExpectedType>::value, "Missing TypeCastTraits specialization");

I cannot use a static_assert(false, ""); because the compiler would then evaluate it and fail the build even if this template was not instantiated. By having the static_assert() depend on the template parameter type, I avoid that issue and we hit the static_assert() only if this is actually instantiated. And this one is only instantiated if there is no specialization for the type.

[WebKit Commit Bot]

Comment on attachment 239067 [details]
Patch

Clearing flags on attachment: 239067

Committed r174193: <http://trac.webkit.org/changeset/174193>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Gyuyoung Kim]

EFL port has been broken since r174193.

https://build.webkit.org/builders/EFL%20Linux%2064-bit%20Release%20WK2/builds/16694

[Chris Dumez]

(In reply to comment #5)
> EFL port has been broken since r174193.
> 
> https://build.webkit.org/builders/EFL%20Linux%2064-bit%20Release%20WK2/builds/16694

Build fix landed in <http://trac.webkit.org/changeset/174195>